PetroChina Co (NYSE: PTR, SHA: 601857, HKG: 0857), the nation's biggest oil explorer, is carrying back its first shipload of two million barrels of crude oil from the Halfaya oilfield in Iraq, PetroChina's parent CNPC said. The Halfaya oilfield, which began production in June with an estimated 4.1 billion barrels of crude reserves, is currently capable of producing five million tons per year, or 100,000 barrels per day. Future expansion will double the annual capacity to 10 million tons. The company's second shipload of crude oil is scheduled to head off to China in January. The Halfaya oilfield is PetroChina's biggest offshore project.